ive taken on a job of replacing all the refrigeration equipment at a very large commercial facility. the business has a maintenance staff that the owners have given me to use for this job. the staff is made up of a wide range of experience, but none includes refrigeration. as such they will have very little to nothing to do with the sealed system, but i would like for them to at least understand defrost termination and defrost timers. i fear i dont make a very good teacher and would very much prefer an online source to at least explain the basics. any help in locating this would be appreciated.